This invention relates to the conversion of methane to higher hydrocarbons. A particular application of this invention is a method for converting natural gas to more readily transportable material.
Recently, it has been discovered that methane may be converted to higher hydrocarbons by a process which comprises contacting methane and an oxidative synthesizing agent at synthesizing conditions (e.g., at a temperature selected within the range from about 500.degree. to about 1000.degree. C.) Oxidative synthesizing agents are compositions having as a principal component at least one oxide of at least one metal which compositions produce C.sub.2 + hydrocarbon products, co-product water, and a composition comprising a reduced metal oxide when contacted with methane at synthesizing conditions. Reducible oxides of several metals have been identified which are capable of converting methane to higher hydrocarbons. In particular, oxides of manganese, tin, indium, germanium, lead, antimony, bismuth, praseodymium, terbium, cerium, iron and ruthenium are most useful. See commonly-assigned U.S. Pat. Nos. 4,443,649 (Mn); 4,444,984 (Sn); 4,445,648 (In); 4,443,645 (Ge); 4,443,674 (Pb); 4,443,646 (Bi); 4,499,323 (Pr); 4,499,324 (Ce); and 4,593,139 (Ru), the entire contents of which are incorporated herein by reference. See also commonly-assigned U.S. patent application Ser. No. 666,694 (Fe) the entire content of which is incorporated herein by reference.
Commonly-assigned U.S. Pat. No. 4,554,395 discloses and claims a process which comprises contacting methane with an oxidative synthesizing agent under elevated pressure (2-100 atmospheres) to produce greater amounts of C.sub.3 + hydrocarbon products
Commonly-assigned U.S. Pat. No. 4,560,821 discloses and claims a process for the conversion of methane to higher hydrocarbons which comprises contacting methane with particles comprising an oxidative synthesizing agent which particles recirculate between two physically separate zones--a methane contact zone and an oxygen contact zone.
U.S. Pat. No. 4,499,322 discloses and claims a process for the conversion of methane to higher hydrocarbon and comprises contacting methane with an oxidative synthesizing agent containing a promoting amount of alkali metal and/or compounds thereof.
U.S. Pat. No. 4,495,374 discloses and claims a process for the conversion of methane to higher hydrocarbons which comprises contacting methane with an oxidative synthesizing agent containing a promoting amount of alkaline earth metal and/or compounds thereof.
Hinsen and Baerns report studies of a continuous mode for the oxidative coupling of methane wherein regeneration air is cofed with methane feed. Hinsen, W. and Baerns, M., "Oxidative Koppling von Methan zu C.sub.2 - Kohlenwasserstoffen in Gegenwart unterschiedlicher Katalsatoren", Chemiker-Zeitung, Vol. 107, No. 718, pp. 223-226 (1983). Using a catalyst based on lead oxide and gamma-alumina in a fixed bed reactor operated at 1 atmosphere total pressure and 600-750 degrees C., they report results of approximately 53% selectivity to ethane and ethylene at 8% methane conversion for a feed consisting of about 50% methane, 25% air and 25% nitrogen. Other metal oxides studies by Hinsen and Baerns included oxides of Bi, Sb, Sn and Mn.
U.S. Pat. No. 4,523,049, discloses and claims a process for converting methane to higher hydrocarbons which comprises contacting methane and an oxygen-containing gas with a solid comprising a reducible metal oxide and an alkali/alkaline earth metal promoter.
U.S. Pat. No. 4,523,050 discloses and claims a process for converting methane to higher hydrocarbons which comprises contacting methane and an oxygen-containing gas with a manganese silicate.
Commonly-assigned U.S. patent application Ser. No. 738,110, filed May 24, 1985, discloses and claims a method for converting methane to higher hydrocarbons wherein methane and a gaseous oxidant are contacted with a nonacidic solid. In a preferred embodiment, the solid comprises an alkali metal component associated with a support material. The application also teaches conducting the contacting in the presence of halogen promoters when employing alk.ali-promoted solids..
Commonly-assigned U.S. patent application Ser. No. 738,114, filed May 24, 1985, discloses and claims a process wherein methane and a gaseous oxidant are contacted with a nonacidic solid in the presence of halogen promoter but in the absence of an alkali metal promoter.
Concurrently-filed, commonly-assigned U.S. patent application Ser. No. 07/014,406 filed 2-13-87 discloses and claims a method for converting methane to higher hydrocarbons wherein methane and added water are contacted in the substantial absence of added gaseous oxidant with a solid comprising at least one reducible metal oxide.
The reaction product of the foregoing processes are hydrocarbons, carbon oxides, coke and water. It would be beneficial in these processes to reduce selectivities to carbon oxides and coke and to increase methane conversions to the desired hydrocarbon products. Accordingly, an object of this invention is to provide an improved process for converting methane to higher hydrocarbons. More particular aspects, objects and the several advantages of this invention will become apparent to those skilled in the art upon reading this disclosure and the appended claims.